<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Document</title>
</head>
<body>
<button id="exportToPdf">导出为PDF</button>
<div id="export_content">
    <div>
        sdsf

    </div>
    <div style="color: red">
        sdsf

    </div>
</div>
</body>
<script src="https://cdn.bootcss.com/jspdf/1.5.3/jspdf.debug.js"></script>
<script src="https://cdn.bootcss.com/html2canvas/0.5.0-beta4/html2canvas.min.js"></script>
<script type="text/javascript">
    var downPdf = document.getElementById("exportToPdf");
    downPdf.onclick = function () {
        html2canvas(
            document.getElementById("export_content"),
            {
                dpi: 172,//导出pdf清晰度
                onrendered: function (canvas) {
                    var contentWidth = canvas.width;
                    var contentHeight = canvas.height;

                    //一页pdf显示html页面生成的canvas高度;
                    var pageHeight = contentWidth / 592.28 * 841.89;
                    //未生成pdf的html页面高度
                    var leftHeight = contentHeight;
                    //pdf页面偏移
                    var position = 0;
                    //html页面生成的canvas在pdf中图片的宽高（a4纸的尺寸[595.28,841.89]）
                    var imgWidth = 595.28;
                    var imgHeight = 592.28 / contentWidth * contentHeight;

                    var pageData = canvas.toDataURL('image/jpeg', 1.0);
                    var pdf = new jsPDF('', 'pt', 'a4');

                    //有两个高度需要区分，一个是html页面的实际高度，和生成pdf的页面高度(841.89)
                    //当内容未超过pdf一页显示的范围，无需分页
                    if (leftHeight < pageHeight) {
                        pdf.addImage(pageData, 'JPEG', 0, 0, imgWidth, imgHeight);
                    } else {
                        while (leftHeight > 0) {
                            pdf.addImage(pageData, 'JPEG', 0, position, imgWidth, imgHeight)
                            leftHeight -= pageHeight;
                            position -= 841.89;
                            //避免添加空白页
                            if (leftHeight > 0) {
                                pdf.addPage();
                            }
                        }
                    }
                    pdf.save('content.pdf');
                },
                //背景设为白色（默认为黑色）
                background: "#fff"
            })
    }
</script>

</html>